Photocatalytic TiO(2) powders impart ultraviolet light-induced self-cleaning and antibacterial functions when coated on outdoor building materials. For indoor applications, however, TiO(2) must be modified for visible-light and dark sensitivity. Here we report that the grafting of nanometer-sized Cu(x)O clusters onto TiO(2) generates an excellent risk-reduction material in indoor environments. X-ray absorption near-edge structure using synchrotron radiation and high-resolution transmission electron microscopic analyses revealed that Cu(x)O clusters were composed of Cu(I) and Cu(II) valence states. The Cu(II) species in the Cu(x)O clusters endow TiO(2) with efficient visible-light photooxidation of volatile organic compounds, whereas the Cu(I) species impart antimicrobial properties under dark conditions. By controlling the balance between Cu(I) and Cu(II) in Cu(x)O, efficient decomposition and antipathogenic activity were achieved in the hybrid Cu(x)O/TiO(2) nanocomposites.